This invention relates to a method of encasing objects, especially ceramic and metal objects.
Because of their high resistance to heat and oxidation, ceramic materials are used to manufacture a wide variety of industrial parts. Often, it is necessary or desirable to encase the ceramic part in metal so that it may be welded to other metal parts. For example, many catalytic converters used in automobiles include a metal or ceramic honeycomb structure, coated with catalyst, which structure is then encased in a metal can so that it may be welded to the automobile chassis. The process commonly used for encasing such catalytic converters in metal is costly and labor intensive. Typically, a piece of metal cut in a clam-shell shape is bent around the previously coated and fired substrate, held in that position and welded closed. Even if the metal casing is tightly fit around the converter at room temperature, the metal will expand differentially from the ceramic at higher temperatures, causing the ceramic to metal fit to loosen, allowing the converter to move within the casing during use and become damaged.
Recently, an improved method has been disclosed for encasing catalytic converters to reduce the effects of differential expansion on the encased object and the metal casing. In particular, it has been suggested to form the metal casing by wrapping a sheet of sinterable particulate metal around a green sinterable object, and firing the wrapped object to form a unitary structure.
There continues to be a need for metal encased articles which can be prepared by less costly and labor intensive methods and which will reduce the effects of differential expansion.